The present invention relates to a fire-resistant glazing assembly composed of at least two glass sheets connected together by a spacer along their edges and of a water-containing interlayer which fills the intermediate space between the glass sheets, the spacer being adhesively bonded to the two glass sheets and the peripheral seal between the spacer and the peripheral regions of the glass sheets being sealed by means of an adhesive sealing material.
Fire-resistant glazing assemblies of this type are known from document EP 0,590,978 A1. In the case of this known fire-resistant glazing assembly, the water-containing interlayer is composed of a hydrogel with a polymer of a methacrylamide derivative acting as gelling agent. The spacer comprises a profiled bead made of a rigid material, namely a metal or ceramic, and butyl rubber acts as adhesive between the spacer and the glass sheets.
The manufacture of fire-resistant glazing assemblies having this structure poses real problems when they use, for example, curved panes. It is in fact difficult to give spacers made of a rigid material a shape such that their bending corresponds exactly to the curving of the panes. Furthermore, the individual curved panes often have shape defects in their peripheral regions. When bonding the two panes together by means of a rigid spacer frame, tensile mechanical stresses may easily occur in the peripheral regions under these conditions, and consequently non-sealed regions may appear in the peripheral regions.
In addition, it has been found that glazing assemblies characterized by this known structure therefore do not always have the desired duration of fire resistance because, in the event of a fire, heat transfer via the frame supporting the fire-resistant glazing assembly in the peripheral zone of the glazing assembly results in tensile stresses which can damage the peripheral region, thereby causing the assembly to break prematurely.
The objective of the invention is to improve the fire-resistant glazing assemblies mentioned in the preamble, in such a way that the peripheral bonding and the sealing in the spacer region are also suitable for the manufacture of non-planar fire-resistant glazing assemblies and at the same time provide better thermal insulation of the edges of the assembly in the event of a fire.
According to the invention, this objective is achieved in that the spacer comprises a profiled bead made of silicone rubber.
Compared with the known fire-resistant glazing assemblies, in the case of the structure according to the invention a spacer composed of an elastic rubber material is used, which material, because of its elasticity, adapts to the irregularities in the glass sheet and easily follows the shape of the panes, even in the case of highly curved panes. Because of the low thermal conductivity of silicone rubber compared with that of a metal, the transfer of heat from the pane exposed to the fire towards the marginal region of the other pane is greatly reduced.
Consequently, the occurrence of thermal gradients that might damage the other pane are avoided or at least greatly reduced.
The fact of using silicone rubber for the spacer has the additional major advantage that, compared with other polymers, no toxic decomposition product is produced in the event of a fire. In addition, silicone rubber is highly heat-resistant and has a very high decomposition temperature. Furthermore, silicone rubber is resistant from a chemical standpoint and is easy to process so that, from the most varied of standpoints, fire-resistant glass produced according to the invention has significant advantages.
Particularly advantageously, spacers made of a high-temperature crosslinkable silicone rubber having a Shore A hardness of 40 to 60 are used. Silicone rubbers of this type have proved to be particularly suitable for achieving the objective of the invention.
Advantageously, a bead composed of a heat-activated foaming material is placed between the spacer and the adhesive sealing material.
The presence of the foaming material in the peripheral seal also acts to reduce the thermal gradients. This is because the foam, which forms under the effect of the heat, fills the fillister region between the edge of the glazing assembly and the frame, which is generally made of metal, and thus significantly decreases the heat transfer from the bottom of the fillister of the metal frame to the edge of the panes of the glazing assembly.